DE102013220407B4 - Method and device for operating an injection valve - Google Patents

Abstract

Method for operating an injection valve (1) comprising an electromagnetic actuator (15) and a valve needle (10) driven by this, which in a closed position prevents metering of fluid and releases metering of fluid outside the closed position and a restoring spring (30), which is coupled to the valve needle (10) and transmits a spring force to the valve needle (10), the electromagnetic actuator (15) having a coil (17), an axially movable armature (20) which can be coupled to the valve needle (10) and a Pole body (23) which is rigidly coupled to a housing (3) of the injection valve (1), in which for a control process for metering fluid the electromagnetic actuator (15) with an increased voltage value in comparison to the rest of the control process (U_B) is applied until a predetermined maximum current value (I_MAX) is reached, - to the electromagnetic actuator (15) after reaching a predetermined e rexpected opening time, at which the valve needle (10) is expected to leave its closed position, a predetermined voltage curve (U_V) is applied until a predetermined expected opening position time (OPZ) is reached, at which the valve needle (10) is expected to reach a predetermined opening position, - a detected opening position time (OPZI) is determined, in which the valve needle (10) reaches the specified opening position, - depending on the detected opening position time (OPZI) the specified voltage curve (U_V) for a further control process is adjusted - with the specified voltage curve (U_V) such is specified that the specified voltage curve (U_V) contributes to the fact that a magnetic force is transmitted to the valve needle (10), which is directed against the spring force and the amount of which corresponds approximately to the amount of the spring force by the current set by means of the specified voltage curve proportionally ional to a reduction in the distance between the armature (20) and the pole body (23).

Description

The invention relates to a method and a device for operating an injection valve comprising an electromagnetic actuator.

Due to ever stricter legal regulations regarding permissible pollutant emissions from internal combustion engines, injection accuracy of injection valves of the internal combustion engine is of central importance.

the DE 196 07 073 A1 discloses a method for controlling the movement of an armature of an electromagnetic switching element which has an excitation winding, in which a first setpoint value for the current can be specified from a first point in time and a second setpoint value can be specified for a second point in time, the second setpoint value being smaller than the first Target value and the second point in time is before a third point in time at which the armature reaches its end position.

the DE 39 23 477 A1 discloses a method for controlling the armature movement of switching magnets, in which the coil current of the electromagnet is regulated linearly before the expected impact of the armature on the pole face in order to detect the impact of the armature on the pole face.

the DE 28 28 678 C2 discloses a method for operating an electromagnetic consumer with a movable armature, in which this consumer is supplied with a high current at the beginning of an actuation signal during the pull-in phase of the armature and a reduced current at the latest towards the end of the actuation signal during the holding phase.

the DE 2004 004 007 A1 discloses a method for operating an internal combustion engine in which, with an initially unknown setpoint gradient of a charging voltage, an adjusted point in time or crankshaft angle for the start of injection for the piezo injector under consideration is determined in such a way that first the current point in time for the start of injection of the piezo -Injector is determined by means of a nominal gradient, which is then compared with a specified reference point in time and then the gradient of the charging voltage or the point in time for the start of injection is corrected according to the size of the difference between the current start of injection and the reference point in time determined during the comparison .

the DE 10 2010 021 169 A1 discloses that with the so-called MFMA method (Minimum Fuel Mass Adaptation), which takes place in specified cycles and under specified boundary conditions during operation, based on measurable system variables, such as the pressure drop in the common rail or the change in rotational speed of the crankshaft for specified test injections , conclusions can be drawn about the fuel quantity actually injected. If this deviates from the fuel quantity expected according to the actuation of the valve, then correction values are determined from this, which are then taken into account for subsequent injections.

the DE 10 2007 051 553 A1 discloses a method for operating an internal combustion engine in which the fuel is injected directly into a combustion chamber by means of an injector and in which at least one operating variable of the internal combustion engine is detected and evaluated and a control variable for the injector is generated. During test operation, the start of an injection is varied systematically by varying the corresponding control variable over time, so that a plurality of work cycles with different starts of injection are carried out. During the test operation, an injection-specific torque or a corresponding variable for the working cycles with different injection starts is recorded or determined. The timing of the control variable is determined, which can be assigned at least approximately to a maximum torque or the corresponding variable (effectively optimal start of injection). Furthermore, a correction variable for the control variable is determined in such a way that, in normal operation, the actual start of injection corresponds at least approximately to the effective-optimal start of injection.

The object on which the invention is based is to provide a method for operating an injection valve and a corresponding device which contributes to achieving high injection accuracy during operation of the injection valve.

The object is solved by the features of the independent patent claims. Advantageous developments of the invention are characterized in the dependent claims.

The invention is distinguished by a method for operating an injection valve. Furthermore, the invention is characterized by a corresponding device for operating the injection valve. The injection valve includes an electromagnetic actuator and a valve needle driven by the latter, which prevents fluid from being metered in a closed position and enables fluid to be metered outside of the closed position. The fuel injector includes a return spring coupled to the valve needle and a spring transmits force to the valve needle. The electromagnetic actuator includes a coil, an axially movable armature that can be coupled to the valve needle, and a pole body that is fixedly coupled to a housing of the injection valve and that forms an axial stop for the armature, for example. For a control process for metering fluid, the electromagnetic actuator is subjected to a voltage value that is increased compared to the remaining control process, until a predetermined maximum current value is reached. After reaching a predetermined expected opening time at which the valve needle is expected to leave its closed position, a predetermined voltage profile is applied to the electromagnetic actuator until a predetermined expected opening position time is reached at which the valve needle is expected to reach a predetermined open position. A detected opening position point in time at which the valve needle reaches the specified opening position is determined. Depending on the detected opening position point in time, the specified voltage curve is adapted for a further control process. The specified voltage curve is specified in such a way that the specified voltage curve contributes to the fact that a magnetic force is transmitted to the valve needle, which is directed counter to the spring force and the amount of which corresponds approximately to the amount of the spring force, in that the current set by means of the predetermined voltage curve is proportional to decrease the distance between the armature and the pole body.

The specified voltage profile is set in particular in such a way that a specified desired current profile is generated, in particular in such a way that the specified current profile is thereby controlled to a respective predefined desired value. If necessary, the current is a controlled variable and the voltage is a manipulated variable.

When the specified opening position is reached, an oscillating course of an opening stroke of the valve needle around the opening position can occur, which is also referred to as an S-shape. The higher the speed of the valve needle when it reaches the predetermined opening position, the greater the oscillation-like course of the opening stroke. The oscillating course of the opening stroke has an influence on an injection quantity in a respective working cycle of the injection valve. Thus, depending on how pronounced the oscillation-like course is, the injected quantity is relatively imprecise, in particular the injected quantity is no longer monotonous as a function of an injection time in this range. The method for operating the injection valve contributes to weakening the oscillation-like curve and thus to achieving a monotonic injection quantity characteristic and thereby achieving a very high injection accuracy during operation of the injection valve. For this purpose, the electromagnetic actuator is first subjected to an increased voltage value in comparison to the remaining control process, so that the injection valve opens quickly. The predetermined voltage curve then contributes to the fact that the valve needle may still not be accelerated, but may be slowed down, so that it gently or relatively gently reaches the predetermined opening position. As a result, the oscillating course of the opening stroke can be weakened, so that a very accurate and very precise injection volume is achieved. By determining the detected opening position time, the specified voltage curve can be adapted for further control processes in such a way that the specified expected opening position time is reached very precisely and/or the specified opening position is reached gently and precisely, in order to enable very precise and precise injection. The specified opening position is in particular an expected valve needle end position, or an opening end position and/or a stop. The predefined expected opening position time is thus in particular an expected valve needle end position time, or an expected opening end position time and/or an expected stop time. The detected opening position time is thus in particular a detected valve needle end position time, or a detected opening end position time and/or a detected stop time.

The predetermined voltage curve contributes in particular to the fact that an expected amount of the spring force corresponds approximately to the amount of the magnetic force.

Specifically, an attractive force of the armature is inversely proportional to a square of a distance between the armature and the pole body, but proportional to a square of a current in the coil. Thus, in particular, the current set by means of the predetermined voltage curve can be reduced proportionally to a reduction in the distance between the armature and the pole body, so that the magnitude of the magnetic force corresponds approximately to the magnitude of the spring force.

This can contribute to the valve needle reaching the specified opening position, in particular a stop, very gently, since the valve needle may pass through the predetermined voltage profile is not further accelerated, but in particular is slowed down by friction and/or hydraulic force. In particular, the specified voltage profile is specified in such a way that shortly before the specified expected opening time is reached, a magnetic force is transmitted to the valve needle that is less than or equal to the magnitude of the spring force.

According to a further advantageous embodiment, after the predetermined maximum current value has been reached, a neutral value of the voltage is applied to the electromagnetic actuator until the expected opening time is reached.

The neutral value of the voltage corresponds, for example, to a voltage of 0 V. By applying a neutral value of the voltage to the electromagnetic actuator, this contributes to the electric actuator generating only a limited amount of energy for a lifting movement of the valve needle, so that no too much energy is transferred to the valve needle, so that the valve needle reaches the expected opening position very smoothly, in particular that the valve needle does not accelerate further after opening to reach the expected opening position.

According to a further advantageous embodiment, after the expected opening position time has been reached, a predetermined ramp-shaped current profile with a positive gradient is applied to the electromagnetic actuator.

In particular, after a threshold value has been reached and/or after a predetermined period of time has elapsed, a plateau-like current profile is then applied to the electric actuator and, for example, a closing process is then initiated.

This can contribute to the needle remaining in the specified open position, despite, for example, possible pressure fluctuations.

According to a further advantageous embodiment, a detected opening time is determined and, depending on the detected opening time, the predefined maximum current value for a further control process is adjusted.

In this way, in particular the length of time between the start of the control process and the point at which the detected opening time is reached can be set, since adapting the predefined maximum current value can contribute to the detected opening time approximately corresponding to the expected opening time. In this way, the same time period between the beginning of the control process and reaching the detected opening time can be set, in particular for a group of injectors of an internal combustion engine.

According to a further advantageous embodiment, the injection valve has an armature which can be coupled to the valve needle and a pole body which is fixedly coupled to a housing of the injection valve. A stop value is determined which is representative of a stop force of the armature on the pole body at the detected opening position time. Depending on the stop value, the specified voltage curve is adjusted for the further control process.

This allows the impact force to be checked, which is representative of the strength of the vibration-like course of the opening stroke. It can thus be set very easily in this way that the strength of the oscillation-like course of the opening stroke is weakened, so that a very accurate and very precise injection volume is achieved.

Exemplary embodiments of the invention are explained in more detail below with reference to the schematic drawings.

• 1 ein Einspritzventil,
• 2 ein Ablaufdiagramm zum Betreiben des Einspritzventils und
• 3A ein Spannungsverlauf im Betrieb des Einspritzventils,
• 3B ein Nadellift im Betrieb des Einspritzventils,
• 3C eine Einspritzmenge im Betrieb des Einspritzventils.

Show it:

• 1 an injector,
• 2 a flowchart for operating the injector and
• 3A a voltage curve during operation of the injection valve,
• 3B a needle lift during operation of the injector,
• 3C an injection quantity during operation of the injection valve.

Elements of the same construction or function are identified with the same reference symbols throughout the figures.

1 shows an injection valve 1 in particular of an internal combustion engine of a vehicle.

The injection valve 1 has a housing 3 with a recess 5. A valve needle 10 is arranged in the recess 5, the valve needle 10 being arranged in the recess 5 in an axially movable manner.

Injection valve 1 also includes an injection opening 12. In a closed position, valve needle 10 prevents fluid from being metered through the injection opening 12. Outside the closed position, the valve needle 10 enables metering of fluid through the injection opening 12.

Injector 1 also includes a restoring spring 30 which is coupled to valve needle 10 and which transmits a spring force to valve needle 10 . In particular, the spring force contributes to holding the valve needle 10 in the closed position.

Injection valve 1 also includes an electromagnetic actuator 15. Electromagnetic actuator 15 is designed to drive valve needle 10. The electromagnetic actuator 15 includes a coil 17. The electric actuator 15 also includes an armature 20. The armature 20 is arranged such that it can move axially in the recess 5 and can be mechanically coupled to the valve needle 10. In particular, the armature 20 can be mechanically coupled to the valve needle 10 in this way that the armature 20 lifts the valve needle 10 out of the closed position when the armature 20 moves axially.

The electric actuator 15 also includes a pole body 23. The pole body 23 is rigidly coupled to the housing 3. In particular, the pole body 23 forms an axial stop for the armature 20.

2 shows a flowchart of a program for operating the injection valve 1, in particular for a control process for metering fluid. The program can be processed by a control device SV, for example.

The program is started in a step S1. In step S1, for example, variables are initialized.

In a step S3, the electromagnetic actuator 15 is subjected to an increased voltage value U_B in comparison to the remaining control process, until a predefined maximum current value I_MAX is reached (see 3A ). The increased voltage value U_B can also be referred to as a boost voltage.

The armature 20 is accelerated very quickly by such a control. Through such a movement of the armature 20, the armature 20 takes the valve needle 10 with it, so that it leaves its closed position (cf 3B and 3C ).

In a step S5, a neutral value U_N of the voltage is applied to the electromagnetic actuator 15 after the predetermined maximum current value I_MAX has been reached until a predetermined expected first opening time is reached, at which the valve needle 10 is expected to leave its closed position. The neutral value U_N corresponds to 0 V, for example.

In a step S7, a predetermined voltage curve U_V is applied to the electromagnetic actuator 15 after the predetermined expected opening time has been reached, until a predetermined expected opening position time OPZ is reached, at which the valve needle 10 is expected to reach a predetermined opening position.

The predetermined voltage curve U_V is particularly predetermined such that the predetermined voltage curve U_V contributes to the fact that a magnetic force is transmitted to the valve needle 10, which is directed against the spring force and whose magnitude corresponds approximately to the magnitude of the spring force.

As a result, the valve needle 10 is not accelerated any further by the specified voltage curve U_V, but rather is slowed down in particular by friction and/or hydraulic force until it reaches the specified opening position (cf 3A , 3B , 3C ).

In an optional step S9, after the expected opening position time OPZ has been reached, a predetermined ramp-shaped current profile I_R with a positive slope is applied to the electromagnetic actuator 15.

In a step S11, a detected opening time OZI is determined and, depending on the detected opening time OZI, the specified maximum current value I_MAX is adjusted for a further control process. Step S11 can, for example, alternatively be carried out in parallel with steps S7, S9.

In a step S13, a detected opening position point in time OPZI is determined, in which the valve needle 10 reaches the specified opening position (see 3a , 3b , 3c ). Depending on the detected opening position point in time OPZI, the specified voltage curve U_V is adapted for the further control process. Alternatively, step S13 can be executed in parallel with steps S9 and/or S11.

Alternatively or additionally, a stop value can optionally be determined which is representative of a stop force of the armature 20 on the pole body 23 at the detected opening position time OPZI. Depending on the stop value, the specified voltage curve U_V can be adjusted for the further control process.

The program is ended in a step S15 and can optionally be started again in step S1.

The procedure explained can contribute to the fact that the specified voltage curve U_V and/or the specified maximum current value I_MAX is adapted for further control processes, so that the specified expected opening time and/or the specified expected opening position time OPZ are reached very precisely, in order to thus to enable monotonous very accurate and precise injection.

Reference List

1

injector

3

Housing

5

recess

10

valve needle

15

electric actuator

17

Kitchen sink

20

anchor

23

polar body

30

return spring

U_B

increased voltage value

U.N

neutral value of the voltage

U_V

predetermined voltage curve

I_R

ramped current flow

I_MAX

maximum current value

OZI

detected opening time

OPZ

Expected opening position time

OPZI

detected opening position time

Claims (6)

Method for operating an injection valve (1) comprising an electromagnetic actuator (15) and a valve needle (10) driven by this, which in a closed position prevents metering of fluid and releases metering of fluid outside the closed position and a restoring spring (30), which is coupled to the valve needle (10) and transmits a spring force to the valve needle (10), the electromagnetic actuator (15) having a coil (17), an axially movable armature (20) which can be coupled to the valve needle (10) and a Pole body (23) comprises, which is fixedly coupled to a housing (3) of the injection valve (1), in which for a control process for the metering of fluid - the electromagnetic actuator (15) is subjected to an increased voltage value (U_B) in comparison to the remaining control process, until a predetermined maximum current value (I_MAX) is reached, - a predetermined voltage curve (U_V) is applied to the electromagnetic actuator (15) after a predetermined expected opening time has been reached, at which the valve needle (10) is expected to leave its closed position, until a predetermined expected opening position time (OPZ) is reached, at which the Valve needle (10) is expected to reach a specified opening position, - a detected opening position time (OPZI) is determined, in which the valve needle (10) reaches the specified opening position, - Depending on the detected opening position time (OPZI), the predetermined voltage curve (U_V) is adapted for a further control process - wherein the predetermined voltage curve (U_V) is predetermined in such a way that the predetermined voltage curve (U_V) contributes to a magnetic force being transmitted to the valve needle (10), which is directed counter to the spring force and whose amount approximately corresponds to the amount of the spring force , in that the current set by means of the predetermined voltage curve is lowered in proportion to a reduction in the distance between the armature (20) and the pole body (23). procedure after claim 1 , in which, after the specified maximum current value (I_MAX) has been reached, until the expected opening time is reached, the electromagnetic actuator (15) is subjected to a neutral value (U_N) of the voltage. Method according to one of the preceding claims, in which, after the expected opening position time (OPZ) has been reached, a predetermined ramp-shaped current profile (I_R) with a positive slope is applied to the electromagnetic actuator (15). Method according to one of the preceding claims, in which a detected opening time (OZI) is determined and depending on the detected opening time (OZI) the specified maximum current value (I_MAX) for a further control process is adjusted. Method according to one of the preceding claims, wherein the injection valve (1) has an armature (20) which can be coupled to the valve needle (10) and a pole body (23) which is fixed to a housing (3) of the injection valve (1). is coupled, in which a stop value is determined which is representative of a stop force of the armature (20) on the pole body (23) at the detected opening position point in time (OPZI) and depending on the stop value the predetermined voltage curve (U_V) is adapted for the further control process becomes. Device for operating an injection valve (1), wherein the device is designed to use a method according to one of Claims 1 until 5 to perform.

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